Templates and macros

The syslog-ng PE application allows you to define message templates, and reference them from every object that can use a template. Templates can include strings, macros (for example, date, the hostname, and so on), and template functions. For example, you can use templates to create standard message formats or filenames. For a list of macros available in syslog-ng Premium Edition, see Macros of syslog-ng PE. Fields from the structured data (SD) part of messages using the new IETF-syslog standard can also be used as macros.

Declaration

Template objects have a single option called template-escape(), which is disabled by default (template-escape(no)). This behavior is useful when the messages are passed to an application that cannot handle escaped characters properly. Enabling template escaping (template-escape(yes)) causes syslog-ng to escape the ', ", and backslash characters from the messages.

If you do not want to enable the template-escape() option (which is rarely needed), you can define the template without the enclosing braces.

template <template-name> "<template-expression>";

You can also refer to an existing template from within a template. The result of the referred template will be pasted into the second template.

template first-template "sample-text";
template second-template "The result of the first-template is: $(template first-template)";

If you want to use a template only once, you can define the template inline, for example:

Macros can be included by prefixing the macro name with a $ sign, just like in Bourne compatible shells. Although using braces around macro names is not mandatory, and the "$MSG" and "${MSG}" formats are equivalent, using the "${MSG}" format is recommended for clarity.

To use a literal $ character in a template, you have to escape it. In syslog-ng PE versions 4.0-4.2, use a backslash (\$). In version 5.0 and later, use $$.

NOTE:

To use a literal @ character in a template, use @@.

Default values for macros can also be specified by appending the :- characters and the default value of the macro. If a message does not contain the field referred to by the macro, or it is empty, the default value will be used when expanding the macro. For example, if a message does not contain a hostname, the following macro can specify a default hostname.

${HOST:-default_hostname}

By default, syslog-ng sends messages using the following template: ${ISODATE} ${HOST} ${MSGHDR}${MSG}\n. (The ${MSGHDR}${MSG} part is written together because the ${MSGHDR} macro includes a trailing whitespace.)

Example: Using templates and macros

The following template (t_demo_filetemplate) adds the date of the message and the name of the host sending the message to the beginning of the message text. The template is then used in a file destination: messages sent to this destination (d_file) will use the message format defined in the template.

Macros can be used to format messages, and also in the name of destination files or database tables. However, they cannot be used in sources as wildcards, for example, to read messages from files or directories that include a date in their name.

Date-related macros

The macros related to the date of the message (for example: ${ISODATE}, ${HOUR}, and so on) have three further variants each:

S_ prefix, for example, ${S_DATE}: The ${S_DATE} macro represents the date found in the log message, that is, when the message was sent by the original application.

Caution:

To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng PE).

R_ prefix, for example, ${R_DATE}: ${R_DATE} is the date when syslog-ng PE has received the message.

C_ prefix, for example, ${C_DATE}: ${C_DATE} is the current date, that is when syslog-ng PE processes the message and resolves the macro. Note that syslog-ng PE evaluates the macro every time it is processed, so even if you use the same macro for the same message, its value can be different. For example, if you use ${C_USEC} in a filter and in a destination filename, their values will be different even for the same message.

The ${DATE} macro equals the ${S_DATE} macro.

The values of the date-related macros are calculated using the original timezone information of the message. To convert it to a different timezone, use the time-zone() option. You can set the time-zone() option as a global option, or per destination. For sources, it applies only if the original message does not contain timezone information. Converting the timezone changes the values of the following date-related macros (macros MSEC and USEC are not changed):

AMPM

DATE

DAY

FULLDATE

HOUR

HOUR12

ISODATE

MIN

MONTH

MONTH_ABBREV

MONTH_NAME

MONTH_WEEK

MSEC

SEC

STAMP

TZ

TZOFFSET

UNIXTIME

USEC

WEEK

WEEK_DAY

WEEK_DAY_ABBREV

WEEK_DAY_NAME

YEAR

YEAR_DAY

Hard versus soft macros

Hard macros contain data that is directly derived from the log message, for example, the ${MONTH} macro derives its value from the timestamp. Hard macros are read-only. Soft macros (sometimes also called name-value pairs) are either built-in macros automatically generated from the log message (for example, ${HOST}), or custom user-created macros generated by using the syslog-ng pattern database or a CSV-parser. In contrast to hard macros, soft macros are writable and can be modified within syslog-ng PE, for example, using rewrite rules.

Hard and soft macros are rather similar and often treated as equivalent. Macros are most commonly used in filters and templates, which does not modify the value of the macro, so both soft and hard macros can be used. However, it is not possible to change the values of hard macros in rewrite rules or via any other means.

The following macros can be modified:FULLHOST_FROM, FULLHOST, HOST_FROM, HOST, LEGACY_MSGHDR, MESSAGE, MSG,MSGID, MSGONLY, PID, PROGRAM, SOURCE. Custom values created using rewrite rules or parsers can be modified as well, just like stored matches of regular expressions ($0 ... $255).

Macros of syslog-ng PE

These macros are available when syslog-ng PE successfully parses the incoming message as a syslog message, or you use some other parsing method and map the parsed values to these macros.

If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

AMPM

Description: Typically used together with the ${HOUR12} macro, ${AMPM} returns the period of the day: AM for hours before mid day and PM for hours after mid day. In reference to a 24-hour clock format, AM is between 00:00-12:00 and PM is between 12:00-24:00. 12AM is midnight. Available in syslog-ng PE 3.2 and later.

BSDTAG

Description: Facility/priority information in the format used by the FreeBSD syslogd: a priority number followed by a letter that indicates the facility. The priority number can range from 0 to 7. The facility letter can range from A to Y, where A corresponds to facility number zero (LOG_KERN), B corresponds to facility 1 (LOG_USER), and so on.

DATE, C_DATE, R_DATE, S_DATE

Description: Date of the message using the BSD-syslog style timestamp format (month/day/hour/minute/second, each expressed in two digits). This is the original syslog time stamp without year information, for example: Jun 13 15:58:00.

DAY, C_DAY, R_DAY, S_DAY

Description: The day the message was sent.

FACILITY

Description: The name of the facility (for example, kern) that sent the message.

FACILITY_NUM

Description: The numerical code of the facility (for example, 0) that sent the message.

FILE_NAME

Description: Name of the log file (including its path) from where syslog-ng PE received the message (only available if syslog-ng PE received the message from a file or a wildcard-file source). If you need only the path or the filename, use the dirname and basename template functions.

FULLDATE, C_FULLDATE, R_FULLDATE, S_FULLDATE

Description: A nonstandard format for the date of the message using the same format as ${DATE}, but including the year as well, for example: 2006 Jun 13 15:58:00.

FULLHOST

Description: The name of the source host where the message originates from.

If the message traverses several hosts and the chain-hostnames() option is on, the first host in the chain is used.

If the keep-hostname() option is disabled (keep-hostname(no)), the value of the $FULLHOST macro will be the DNS hostname of the host that sent the message to syslog-ng PE (that is, the DNS hostname of the last hop). In this case the $FULLHOST and $FULLHOST_FROM macros will have the same value.

If the keep-hostname() option is enabled (keep-hostname(yes)), the value of the $FULLHOST macro will be the hostname retrieved from the log message. That way the name of the original sender host can be used, even if there are log relays between the sender and the server.

NOTE:

The use-dns(), use-fqdn(), normalize-hostnames(), and dns-cache() options will have no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

FULLHOST_FROM

Description: The FQDN of the host that sent the message to syslog-ng as resolved by syslog-ng using DNS. If the message traverses several hosts, this is the last host in the chain.

The syslog-ng PE application uses the following procedure to determine the value of the $FULLHOST_FROM macro:

The syslog-ng PE application takes the IP address of the host sending the message.

If the use-dns() option is enabled, syslog-ng PE attempts to resolve the IP address to a hostname. If it succeeds, the returned hostname will be the value of the $FULLHOST_FROM macro. This value will be the FQDN of the host if the use-fqdn() option is enabled, but only the hostname if use-fqdn() is disabled.

If the use-dns() option is disabled, or the address resolution fails, the ${FULLHOST_FROM} macro will return the IP address of the sender host.

HOUR, C_HOUR, R_HOUR, S_HOUR

HOUR12, C_HOUR12, R_HOUR12, S_HOUR12

Description: The hour of day the message was sent in 12-hour clock format. See also the ${AMPM} macro. 12AM is midnight. Available in syslog-ng PE 3.2 and later.

HOST

Description: The name of the source host where the message originates from.

If the message traverses several hosts and the chain-hostnames() option is on, the first host in the chain is used.

If the keep-hostname() option is disabled (keep-hostname(no)), the value of the $HOST macro will be the DNS hostname of the host that sent the message to syslog-ng PE (that is, the DNS hostname of the last hop). In this case the $HOST and $HOST_FROM macros will have the same value.

If the keep-hostname() option is enabled (keep-hostname(yes)), the value of the $HOST macro will be the hostname retrieved from the log message. That way the name of the original sender host can be used, even if there are log relays between the sender and the server.

NOTE:

The use-dns(), use-fqdn(), normalize-hostnames(), and dns-cache() options will have no effect if the keep-hostname() option is enabled (keep-hostname(yes)) and the message contains a hostname.

HOST_FROM

Description: The FQDN of the host that sent the message to syslog-ng as resolved by syslog-ng using DNS. If the message traverses several hosts, this is the last host in the chain.

The syslog-ng PE application uses the following procedure to determine the value of the $HOST_FROM macro:

The syslog-ng PE application takes the IP address of the host sending the message.

If the use-dns() option is enabled, syslog-ng PE attempts to resolve the IP address to a hostname. If it succeeds, the returned hostname will be the value of the $HOST_FROM macro. This value will be the FQDN of the host if the use-fqdn() option is enabled, but only the hostname if use-fqdn() is disabled.

If the use-dns() option is disabled, or the address resolution fails, the ${HOST_FROM} macro will return the IP address of the sender host.

ISODATE, C_ISODATE, R_ISODATE, S_ISODATE

Description: Date of the message in the ISO 8601 compatible standard timestamp format (yyyy-mm-ddThh:mm:ss+-ZONE), for example: 2006-06-13T15:58:00.123+01:00. If possible, it is recommended to use ${ISODATE} for timestamping. Note that syslog-ng can produce fractions of a second (for example, milliseconds) in the timestamp by using the frac-digits() global or per-destination option.

LEVEL_NUM

Description: The priority (also called severity) of the message, represented as a numeric value, for example, 3. For the textual representation of this value, use the ${LEVEL} macro. See PRIORITY or LEVEL for details.

LOGHOST

Description: The hostname of the computer running syslog-ng PE — it returns the same result as the hostname command.

MESSAGE

Description: Text contents of the log message without the program name and pid. The program name and the pid together are available in the ${MSGHDR} macro, and separately in the ${PROGRAM} and ${PID} macros.

If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).

The ${MSG} macro is an alias of the ${MESSAGE} macro: using ${MSG} in syslog-ng PE is equivalent to ${MESSAGE}.

Note that before syslog-ng version 3.0, the ${MESSAGE} macro included the program name and the pid. In syslog-ng 3.0, the ${MESSAGE} macro became equivalent with the ${MSGONLY} macro.

MIN, C_MIN, R_MIN, S_MIN

Description: The minute the message was sent.

MONTH, C_MONTH, R_MONTH, S_MONTH

Description: The month the message was sent as a decimal value, prefixed with a zero if smaller than 10.

MONTH_ABBREV, C_MONTH_ABBREV, R_MONTH_ABBREV, S_MONTH_ABBREV

Description: The English abbreviation of the month name (3 letters).

MONTH_NAME, C_MONTH_NAME, R_MONTH_NAME, S_MONTH_NAME

Description: The English name of the month name.

MONTH_WEEK, C_MONTH_WEEK, R_MONTH_WEEK, S_MONTH_WEEK

Description: The number of the week in the given month (0-5). The week with numerical value 1 is the first week containing a Monday. The days of month before the first Monday are considered week 0. For example, if a 31-day month begins on a Sunday, then the 1st of the month is week 0, and the end of the month (the 30th and 31st) is week 5.

MSEC, C_MSEC, R_MSEC, S_MSEC

Description: The millisecond the message was sent.

Available in syslog-ng PE version 4 F2 and later.

MSG

The ${MSG} macro is an alias of the ${MESSAGE} macro, using ${MSG} in syslog-ng PE is equivalent to ${MESSAGE}. For details on this macro, see MESSAGE.

MSGHDR

Description: The name and the PID of the program that sent the log message in PROGRAM[PID]: format. Includes a trailing whitespace. Note that the macro returns an empty value if both the PROGRAM and PID fields of the message are empty.

MSGID

Description: A string specifying the type of the message in IETF-syslog (RFC5424-formatted) messages. For example, a firewall might use the ${MSGID} "TCPIN" for incoming TCP traffic and the ${MSGID} "TCPOUT" for outgoing TCP traffic. By default, syslog-ng PE does not specify this value, but uses a dash (-) character instead. If an incoming message includes the ${MSGID} value, it is retained and relayed without modification.

MSGONLY

Description: Message contents without the program name or pid. Starting with syslog-ng PE 3.0, the following macros are equivalent: ${MSGONLY}, ${MSG}, ${MESSAGE}. For consistency, use the ${MESSAGE} macro. For details, see MESSAGE.

PID

Description: The PID of the program sending the message.

PRI

Description: The priority and facility encoded as a 2 or 3 digit decimal number as it is present in syslog messages.

PRIORITY or LEVEL

Description: The priority (also called severity) of the message, for example, error. For the textual representation of this value, use the ${LEVEL} macro. See PRIORITY or LEVEL for details.

PROGRAM

Description: The name of the program sending the message. Note that the content of the ${PROGRAM} variable may not be completely trusted as it is provided by the client program that constructed the message.

RAWMSG

Description: The original message as received from the client. Note that this macro is available only in 7.0.9 and later, and only if syslog-ng received the message using the default-network-drivers-ng() source, or the source receiving the message has the store-raw-message flag set.

RCPTID

Description: When the use-rcptid global option is set to yes, syslog-ng PE automatically assigns a unique reception ID to every received message. You can access this ID and use it in templates via the ${RCPTID} macro. The reception ID is a monotonously increasing 48-bit integer number, that can never be zero (if the counter overflows, it restarts with 1).

RUNID

Description: An ID that changes its value every time syslog-ng PE is restarted, but not when reloaded.

SDATA, .SDATA.SDID.SDNAME

Description: The syslog-ng application automatically parses the STRUCTURED-DATA part of IETF-syslog messages, which can be referenced in macros. The ${SDATA} macro references the entire STRUCTURED-DATA part of the message, while structured data elements can be referenced using the ${.SDATA.SDID.SDNAME} macro.Available only in syslog-ng Premium Edition 4.0 and later.

NOTE:

When using STRUCTURED-DATA macros, consider the following:

When referencing an element of the structured data, the macro must begin with the dot (.) character. For example, ${.SDATA.timeQuality.isSynced}.

The SDID and SDNAME parts of the macro names are case sensitive: ${.SDATA.timeQuality.isSynced} is not the same as ${.SDATA.TIMEQUALITY.ISSYNCED}.

Example: Using SDATA macros

For example, if a log message contains the following structured data: [exampleSDID@0 iut="3" eventSource="Application" eventID="1011"][examplePriority@0 class="high"] you can use macros like: ${.SDATA.exampleSDID@0.eventSource} — this would return the Application string in this case.

SEC, C_SEC, R_SEC, S_SEC

Description: The second the message was sent.

SEQNUM

Description: The ${SEQNUM} macro contains a sequence number for the log message. The value of the macro depends on the scenario, and can be one of the following:

If syslog-ng PE receives a message via the IETF-syslog protocol that includes a sequence ID, this ID is automatically available in the ${SEQNUM} macro.

If the message is a Cisco IOS log message using the extended timestamp format, then syslog-ng PE stores the sequence number from the message in this macro. If you forward this message the IETF-syslog protocol, syslog-ng PE includes the sequence number received from the Cisco device in the ${.SDATA.meta.sequenceId} part of the message.

NOTE:

To enable sequence numbering of log messages on Cisco devices, use the following command on the device (available in IOS 10.0 and later): service sequence-numbers. For details, see the manual of your Cisco device.

For locally generated messages (that is, for messages that are received from a local source, and not from the network), syslog-ng PE calculates a sequence number when sending the message to a destination (it is not calculated for relayed messages).

The sequence number is not global, but per-destination. Essentially, it counts the number of messages sent to the destination.

This sequence number increases by one for every message sent to the destination. It not lost when syslog-ng PE is reloaded, but it is reset when syslog-ng PE is restarted.

This sequence number is added to every message that uses the IETF-syslog protocol (${.SDATA.meta.sequenceId}), and can be added to BSD-syslog messages using the ${SEQNUM} macro.

NOTE:

If you need a sequence number for every log message that syslog-ng PE receives, use the RCPTID macro.

SOURCE

Description: The identifier of the source statement in the syslog-ng PE configuration file that received the message. For example, if syslog-ng PE received the log message from the source s_local { internal(); }; source statement, the value of the ${SOURCE} macro is s_local. This macro is mainly useful for debugging and troubleshooting purposes.

SOURCEIP

Description: IP address of the host that sent the message to syslog-ng. (That is, the IP address of the host in the ${FULLHOST_FROM} macro.) Please note that when a message traverses several relays, this macro contains the IP of the last relay.

STAMP, R_STAMP, S_STAMP

Description: A timestamp formatted according to the ts-format() global or per-destination option.

SYSUPTIME

Description: The time elapsed since the syslog-ng PE instance was started (that is, the uptime of the syslog-ng PE process). The value of this macro is an integer containing the time in 1/100th of the second.

Note that syslog-ng PE evaluates the macro every time it is processed, so even if you use the same macro for the same message, its value can be different. For example, if you use it in a filter and in a destination filename, their values will be different even for the same message.

Available in syslog-ng PE version 4 F1 and later.

TAG

Description: The priority and facility encoded as a 2 digit hexadecimal number.

TAGS

Description: A comma-separated list of the tags assigned to the message. Available only in syslog-ng Premium Edition 3.2 and later.

NOTE:

Note that the tags are not part of the log message and are not automatically transferred from a client to the server. For example, if a client uses a pattern database to tag the messages, the tags are not transferred to the server. A way of transferring the tags is to explicitly add them to the log messages using a template and the ${TAGS} macro, or to add them to the structured metadata part of messages when using the IETF-syslog message format.

When sent as structured metadata, it is possible to reference to the list of tags on the central server, and for example, to add them to a database column.